ANTENNA DEVICE AND WIRELESS COMMUNICATION APPARATUS

• US 20090115674A1
• Filed: 01/13/2009
• Published: 05/07/2009
• Est. Priority Date: 07/13/2006
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Fujieda, Shigeyuki, Kawahata, Kazunari, Ishizuka, Kenichi
• Granted Patent: US 8,508,420 B2
• Time in Patent Office: Days
• US Class Current: 343/745
• CPC Class Codes: H01Q 1/243 with built-in antennas
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 5/321 within a radiating element or between connected radiating elements
• CPC Class Codes: H01Q 5/371 Branching current paths
• CPC Class Codes: H01Q 9/0442 with particular tuning means
• CPC Class Codes: H01Q 9/145 by varying the electrical length
• CPC Class Codes: H01Q 9/40 Element having extended radiating surface
• CPC Class Codes: H01Q 9/42 with folded element, the folded parts being spaced apart a small fraction of the operating wavelength

Abstract

An antenna device and a wireless communication apparatus that are capable of obtaining a plurality of resonant frequencies and varying the plurality of resonant frequencies over a wide range are provided. A first antenna unit of an antenna device includes a feed electrode, a first radiation electrode, and a first frequency-variable circuit. The first frequency-variable circuit includes first and second reactance circuits each including a variable-capacitance diode. A control voltage is applied to the first frequency-variable circuit, and the resonant frequency of the first antenna unit can thus be varied. A second antenna unit includes the feed electrode, a second radiation electrode, and a second frequency-variable circuit. The second frequency-variable circuit includes first and third reactance circuits each including a variable-capacitance diode. A control voltage is applied to the second frequency-variable circuit, and the resonant frequency of the second antenna unit can thus be varied.

Claims

1. An antenna device comprising a first antenna unit including a feed electrode, a first radiation electrode, and a first frequency-variable circuit connected between the first radiation electrode and the feed electrode;

and a second antenna unit including the feed electrode, a second radiation electrode, and a second frequency-variable circuit connected between the second radiation electrode and the feed electrode,

wherein the first frequency-variable circuit includes a first reactance circuit connected to the feed electrode, the first reactance circuit including a first variable-capacitance diode whose capacitance is variable using a control voltage; and

a second reactance circuit connected between the first reactance circuit and the first radiation electrode, the second reactance circuit including a second variable-capacitance diode whose capacitance is variable using the control voltage, and

wherein the second frequency-variable circuit includes the first reactance circuit; and

a third reactance circuit connected between the first reactance circuit and the second radiation electrode, the third reactance circuit including a third variable-capacitance diode whose capacitance is variable using the control voltage.

2. The antenna device according to claim 1, wherein the second variable-capacitance diode of the second reactance circuit and the third variable-capacitance diode of the third reactance circuit are disposed so as to associate with the first variable-capacitance diode of the first reactance circuit, with cathodes of the first to third variable-capacitance diodes being connected to each other, and the control voltage is applied to a portion where the cathodes are connected to each other.

3. The antenna device according to claim 2, wherein:

the first reactance circuit is a series resonant circuit or a parallel resonant circuit including the first variable-capacitance diode;

the second reactance circuit is a series resonant circuit or a parallel resonant circuit including the second variable-capacitance diode; and

the third reactance circuit is a series resonant circuit or a parallel resonant circuit including the third variable-capacitance diode.

4. The antenna device according to claim 3, wherein:

each of the first to third reactance circuits is configured as a parallel resonant circuit in which a coil is connected in parallel to a series circuit including the corresponding variable-capacitance diode; and

at least one of the coils of the first to third reactance circuits is a choke coil such that the corresponding reactance circuit including the coil is a series resonant circuit.

5. The antenna device according to claim 1, wherein:

the first reactance circuit is a series resonant circuit or a parallel resonant circuit including the first variable-capacitance diode;

the second reactance circuit is a series resonant circuit or a parallel resonant circuit including the second variable-capacitance diode; and

the third reactance circuit is a series resonant circuit or a parallel resonant circuit including the third variable-capacitance diode.

6. The antenna device according to claim 5, wherein:

each of the first to third reactance circuits is configured as a parallel resonant circuit in which a coil is connected in parallel to a series circuit including the corresponding variable-capacitance diode; and

at least one of the coils of the first to third reactance circuits is a choke coil such that the corresponding reactance circuit including the coil is a series resonant circuit.

7. The antenna device according to claim 1, wherein an internal resistance of at least one of the first to third variable-capacitance diodes is different from internal resistances of the others of the first to third variable-capacitance diodes.

8. The antenna device according to claim 1, wherein at least the first antenna unit is formed on a dielectric substrate.

9. The antenna device according to claim 1, wherein an additional antenna unit is formed by an additional radiation electrode, the feed electrode, and said first frequency-variable circuit, which comprises said first reactance circuit.

10. The antenna device according to claim 1, comprising:

a plurality of additional antenna units; and

at least one of the plurality of additional antenna units comprises an additional radiation electrode, and an additional reactance circuit including a variable-capacitance diode whose capacitance is variable using the control voltage;

said additional reactance unit being connected between the first reactance circuit and the corresponding additional radiation electrode, and a frequency-variable circuit of said at least one of the plurality of additional antenna units is formed by the additional reactance circuit and the first reactance circuit.

11. A wireless communication apparatus comprising an antenna device comprising a first antenna unit including a feed electrode, a first radiation electrode, and a first frequency-variable circuit connected between the first radiation electrode and the feed electrode;

and a second antenna unit including the feed electrode, a second radiation electrode, and a second frequency-variable circuit connected between the second radiation electrode and the feed electrode,

wherein the first frequency-variable circuit includes a first reactance circuit connected to the feed electrode, the first reactance circuit including a first variable-capacitance diode whose capacitance is variable using a control voltage; and

a second reactance circuit connected between the first reactance circuit and the first radiation electrode, the second reactance circuit including a second variable-capacitance diode whose capacitance is variable using the control voltage, and

wherein the second frequency-variable circuit includes the first reactance circuit; and

a third reactance circuit connected between the first reactance circuit and the second radiation electrode, the third reactance circuit including a third variable-capacitance diode whose capacitance is variable using the control voltage; and

a transmitter/receiver connected to said feed electrode.

12. A wireless communication apparatus according to claim 11, further comprising a frequency controller supplying said control voltage to said antenna device.